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Individual study: Effects of spring and autumn fires on the composition of Chionochloa rigida tussock grassland on Flagstaff Hill, Otago, New Zealand

Published source details

Allen R.B & Partridge T.R. (1988) Effects of spring and autumn fires on the composition of Chionochloa rigida tussock grassland, New Zealand. Vegetatio (now Plant Ecology). Plant Ecology, 37-44



In parts of South Island (New Zealand), large areas of montane Chionochloa rigida snow tussock grassland have developed over hundreds of years in response to anthropogenic fires and concurrent native forest loss. At Flagstaff Hill (45°50'S, 170°27 'E; 668 m) on the outskirts of Dunedin City (Otago) an accidental fire burned 70 ha in autumn (March) 1976. Subsequently another 20 ha was deliberately burnt in spring (September) 1976 to assess the potential of prescribed burning to perpetuate narrow-leaved snow tussock C.rigida grassland for nature conservation purposes.


Both burnt areas had similar plant species cover and composition prior to burning (C.rigida snow tussock dominated with much New Zealand flax Phormium cookianum). Species cover and frequency were recorded in October 1977 (19 and 13 months after the fires) andin summer 1985-86. Five 30 m transects within an area approximately 150 x 100 m on each burn site were established. Twenty 1.5 x 1.5 m quadrats were placed along each transect, within which vascular plants, litter, bare soil, rock and cryptogams (mosses, liverworts and lichens), and frequency of vascular plants, was recorded.


In 1977, litter cover was significantly lower (14.8 vs. 71.7%) and bare soil significantly greater (48.6 vs. 0.6%), vascular plant cover was greater (35.3 vs. 25.8%) and cryptogram cover lower (0.2 vs. 1.2%), on the autumn compared with spring burn site. By 1985 cover values at autumn and spring burn sites had converged with marked decreases in bare soil (almost zero) and increases in vascular plant cover: litter (23.9 vs. 35.7%), bare soil (both 0.1%), vascular plants (74.7 vs. 62.7%) and cryptograms (0.5 vs.2.5%).
Overall, Chionochloa cover increased significantly between 1977 and 1985 (10.0 to 33.5%), but cover of the two other large-tussock forming dominants, Phormium (10.0 vs. 10.5%)and Astelia nervosa (10.4 vs. 9.5%)remained about the same. Astelia cover remained significantly lower on the autumn burned site (5.3 vs. 13.6%)
In 1985, cover and frequencies were similar for most species on both sites. Recovery in size of native tussock species (e.g. Chionochloa) suppressed inter-tussock shrubs, herbs and grasses (including the dominant non-native, common bent Agrostis capillaris) that had initially increased through reduction in competition following burning. Overall, there was negligible change in frequency between 1977 and 1985 of species contributing 5% cover or more of the grassland.

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